<!DOCTYPE html>
<html lang="en">
 
 <head>
 <meta charset="UTF-8">
 <title>manga</title>
 <style>
  * {
  padding: 0px;
  margin: 0px;
  }
   
  html,
  body {
  width: 100%;
  min-height: 100%;
  }
   
  #SB {
  margin: 0;
  padding: 0;
  list-style: none;
  }
   
  #SB .in {
  border: 1px solid red;
  margin: 10px;
  text-align: center;
  height: 400px;
  width: 400px;
  float: left;
  }
   
  .in img {
  border: none;
  vertical-align: middle;
  height: 400px;
  width: 400px;
  }
 </style>
 </head>
 
 <body>
 <ul id="SB">
  <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F001.png&quality=90&size=c256_u256"></li>
   <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F002.png&quality=90&size=c256_u256"></li>
     <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F003.png&quality=90&size=c256_u256"></li>
       <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F004.png&quality=90&size=c256_u256"></li>
         <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F005.png&quality=90&size=c256_u256"></li>
   <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F006.png&quality=90&size=c256_u256"></li>
     <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F007.png&quality=90&size=c256_u256"></li>
       <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F008.png&quality=90&size=c256_u256"></li>
         <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F009.png&quality=90&size=c256_u256"></li>
           <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F010.png&quality=90&size=c256_u256"></li>
             <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F011.png&quality=90&size=c256_u256"></li>
               <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F012.png&quality=90&size=c256_u256"></li>
                 <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F013.png&quality=90&size=c256_u256"></li>
                   <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F014.png&quality=90&size=c256_u256"></li>
                     <li class="in"><img src="https://pcs.baidu.com/rest/2.0/pcs/thumbnail?method=generate&app_id=250528&path=%2FSHAR%2Fmanga%2Ffate-grand_order-1-riyu%2F015.png&quality=90&size=c256_u256"></li>
 </ul>
 <script type="text/javascript">
  var aImages = document.getElementById("SB").getElementsByTagName('img'); //获取id为SB的文档内所有的图片
  loadImg(aImages);
  window.onscroll = function() { //滚动条滚动触发
  loadImg(aImages);
  };
  //getBoundingClientRect 是图片懒加载的核心
  function loadImg(arr) {
  for(var i = 0, len = arr.length; i < len; i++) {
   if(arr[i].getBoundingClientRect().top < document.documentElement.clientHeight && !arr[i].isLoad) {
   arr[i].isLoad = true; //图片显示标志位
   //arr[i].style.cssText = "opacity: 0;"; 
   (function(i) {
    setTimeout(function() {
    if(arr[i].dataset) { //兼容不支持data的浏览器
     aftLoadImg(arr[i], arr[i].dataset.imgurl);
    } else {
     aftLoadImg(arr[i], arr[i].getAttribute("data-imgurl"));
    }
    arr[i].style.cssText = "transition: 1s; opacity: 1;" //相当于fadein
    }, 500)
   })(i);
   }
  }
  }
 
  function aftLoadImg(obj, url) {
  var oImg = new Image();
  oImg.onload = function() {
   obj.src = oImg.src; //下载完成后将该图片赋给目标obj目标对象
  }
  oImg.src = url; //oImg对象先下载该图像
  }
 </script>
 </body>
 
</html>